. and you can already sense in the crowds the special energy of the home stretch. but tonight, surprisingly, and in contrast to the daily scrap on the trail, no zingers, no roundhouse punches. hardly any humor. instead, long answers, sometimes dense arguments. the president struggled to score points on what polls show is romney's biggest vulnerability. most voters believe he favors the rich. and obama tried to portray the romney/ryan plan for medicare in that light. >> when you move to a voucher system, you are putting seniors at the mercy of those insurance companies. and over time, if traditional medicare has decayed or fallen apart, then they're stuck. >> reporter: for his part, romney zeroed in on what may be obama's big vulnerability, the unpopularity of his health care plan and the sense that he took his eye off the economic ball when he pushed for it. >> i just don't know how the president could have come into office, facing 23 million people out of work, rising unemployment, an economic crisis at the kitchen table and spend his energy and passion for two years fighting